The present invention relates generally to the art of fluid absorption and more particularly to a disposable sanitary napkin that is thin, highly absorbent and is capable of controlled deformation when in use.
One element that contributes to the performance of a sanitary napkin is the way the napkin withstands deformation when in use. It has been observed that the thighs of an individual exert lateral forces on a sanitary napkin when the article is positioned for use on the undergarment. This results in bunching of the sanitary napkin, affecting the efficiency of the article""s ability to collect bodily fluids since there is a concomitant reduction in the article""s surface area. This observation is especially true for thin sanitary napkins that are highly flexible.
One approach to minimising this problem is to make the sanitary napkin stiffer in order that it may better withstand the effects of lateral compression. This approach may, however, have an adverse effect on the comfort potential of the sanitary napkin because the added stiffness affects the movement of the napkin in all directions, making it more difficult for the napkin to conform to the natural shape of the wearer""s body.
Against this background, it can be seen that there exists a need to provide a sanitary napkin that is comfortable and yet reduces the likelihood of bunching when in use, leading to an overall increase in its efficiency for collecting bodily fluids.
It has been discovered that when a sanitary napkin is provided with at least one preferential bending zone in its absorbent system, the effect is to promote the folding of the absorbent system along this preferential zone and to promote a certain three-dimensional deformation profile in the napkin in response to lateral compression exerted by the thighs of the wearer. The sanitary napkin has a flexural resistance that is not less than about 400 g. This feature provides a sanitary napkin that is sufficiently stiff, so as to be stable enough and thus allow the sanitary napkin to fold in a predictable manner and avoid the likelihood of bunching when subjected to lateral compression.
In one aspect of the invention, the absorbent system of the sanitary napkin includes two preferential bending zones extending longitudinally near the side edges of the napkin and a central preferential bending zone extending longitudinally in the central portion of the absorbent system. In use, the sanitary napkin assumes a three-dimensional deformation profile that resembles the letter xe2x80x9cWxe2x80x9d, in response to the lateral forces exerted by the thighs of the wearer. In a specific example of implementation, the sanitary napkin includes a plurality of preferential bending lines that extend obliquely relative to the longitudinal axis of the napkin and intersect each other. The preferential bending lines cross one another and form an array of crossing points. The crossing points are located along the longitudinal axis of the sanitary napkin and structurally weaken the sanitary napkin at that location allowing the sanitary napkin to fold preferentially along its longitudinal axis. The array of crossing points forms the central preferential bending zone.
The preferential bending zone under any one of the aspects of the invention presented above may be realised by means of any one of the following: perforations, slits, cuts and embossing, as well as any other processes known to a person skilled in the art that has the effect of locally weakening the material in which the preferential bending zone is to be created.
Other aspects and features of the present invention will become apparent in those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.